I would like to block the entire member list of a Facebook group, which I do not belong to, all at once. Is that even possible?
The only option provided in the Facebook Help Center page How do I remove or block someone from a group? has instructions for removing a single member at a time. At this point in time, there is no way to remove multiple users from a group easily.
There are some suggestions on the Facebook Help Community such as the question How to remove multiple members from a group at once? which uses third party tools to remove multiple users, but that is not supported by Facebook and does not include blocking users.